Device for manually unlocking a holding mechanism to which a load can be applied

ABSTRACT

The invention relates to a device ( 50 ) for manually unlocking a holding mechanism ( 10 ) to which a load can be applied, comprising an operating element ( 62 ) which is to be operated manually for unlocking the holding mechanism ( 10 ) with an operating force becoming larger as the load increases, a conversion mechanism ( 64, 90 ) which includes a force transfer element ( 72 ) coupled to the operating element ( 62 ), and a trigger ( 66 ) coupled to the force transfer element ( 72 ), wherein in order to unlock the holding mechanism ( 10 ) the trigger is movable by the operating force transferred by the force transfer element ( 72 ) to the trigger ( 66 ) from a locked position in which the trigger ( 66 ) is operatively decoupled from the holding mechanism into an unlocked position in which the trigger ( 66 ) is operatively coupled to the holding mechanism in order to unlock said holding mechanism. The conversion mechanism ( 64, 90 ) includes an elastically deformable force limiter ( 80 ) via which the force transfer element ( 72 ) is coupled to the trigger ( 66 ) and which prevents the transfer of the operating force to the trigger ( 66 ) due to the elastic deformation thereof, if the operating force exceeds a predetermined force.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is entitled to the benefit of and incorporates byreference subject matter disclosed in International Patent ApplicationNo. PCT/EP2013/052408 filed on Feb. 7, 2013 and German PatentApplication No. 10201200970.8 filed Feb. 7, 2012.

TECHNICAL FIELD

The invention relates to a device for manually unlocking a holdingmechanism to which a load can be applied, comprising an operatingelement which is to be operated manually for unlocking the holdingmechanism with an operating force becoming larger as the load increases,a conversion mechanism which includes a force transfer element coupledto the operating element, and a trigger coupled to the force transferelement, wherein in order to unlock the holding mechanism the trigger ismovable by the operating force transferred by the force transfer elementto the trigger from a locked position in which the trigger isoperatively decoupled from the holding mechanism into an unlockedposition in which the trigger is operatively coupled to the holdingmechanism in order to unlock said holding mechanism.

BACKGROUND

In medical technology recently a mechanical assistance system is used,e.g. for supporting the arm in operations at the shoulder or at theupper arm of a patient. This assistance system is substantially formedby a holding arm, which is illustrated purely schematically in FIG. 1.

The holding arm referred to with 10 in FIG. 1 includes a plurality ofrigid holding members 12, 14, 16, 18, 20 and 22 which are coupledtogether via joints 24, 26, 28, 30 and 32. At one end of the holding arm10 a fixing device 34 is arranged which serves to attach the holding arm10 at a sliding rail of an operating table. At the other end of theholding arm 10 a handle 36 is positioned which can be manually operatedby the operator to unlock the holding arm 10 in the manner describedbelow. At the handle 36 a holder 40 provided with a plurality of latchopenings 38 is attached at which a not shown support, e.g. forsupporting the patient's arm, can be attached.

As mentioned above, the handle 36 serves to unlock the holding arm 10,in particular the joints 24 to 32 coupling the individual holdingmembers 12 to 22 together. For this, the handle 36 includes a mechanicaltrigger, not shown in FIG. 1, which upon compressing the handle 36operates an unlocking rod system, not shown in FIG. 1, guided throughthe holding arm 10. In doing so, the operating force exerted on thehandle 36 is transferred via a conversion mechanism, which is positionedinside the handle 36, to the trigger. If the trigger due to theoperation of the handle 36 acts on the rod system, the latter ensuresthat the individual joints 24 to 32 are unlocked. Each of the joints 24to 32 is formed such that it allows in the unlocked state a relativemovement of the two holding members which are coupled to each other bysaid joint.

If no operating force is exerted on the handle 36, the holding members12 to 22 of the holding arm 10 are rigidly coupled to each other via thejoints 24 to 32. In this state, the holding arm 10 forms a rigid unitwhich is suited to support the patient's arm in a stable position. Ifthe position of the patient's arm in the space shall be changed, theoperator compresses the handle 36 causing the unlocking mechanism to beoperated via the mechanical trigger. By operating the handle 36 theholding members 12 to 22 coupled to each other via the joints 24 to 32become thus movable relative to each other, so that the operator canalign the holding arm 10 as desired. If the operator subsequentlyreleases the handle 36 again, the joints 24 to 32 are locked again andthe holding arm 10 is fixed again in its changed alignment.

The operating force which the operator has to exert on the handle 36 inorder to unlock the holding arm 10 depends on the load which is appliedto the holding arm 10. This load is composed of the proper weight of theholding arm 10 and the weight of the supported patient's arm. Theheavier the patient's arm is, the larger the operating forceconsequently has to be, which the operator has to exert on the handle 36in order to unlock the holding arm 10.

If the operator operates the handle 36 with a sufficiently largeoperating force, the holding arm 10 is promptly unlocked. This meansthat the holding arm 10 instantly yields under the load, i.e.substantially the weight of the patient's arm. This yielding of theholding arm 10 is less problematic as far as the weight supported on theholding arm 10 is relatively low. In this case, the operator cancounteract a sudden bagging of the holding arm 10 by exerting with hishand holding the handle 26 a counteracting force opposite to the weightof the patient's arm, i.e. he generally pushes the handle 36 a littleupwards since the load acts downwards.

However, if the weight of the supported patient is relatively large, theoperator has to exert a correspondingly large counteracting force afterunlocking the holding arm 10 to stabilize the holding arm 10. As theunlocking of the holding arm 10 occurs promptly, the operator has toreact quickly, which renders handling of the holding arm 10 difficult.Now, the operator can prevent an abrupt bagging of the holding arm 10from the very beginning by supporting the holding arm 10 from below withhis one hand, while operating the handle 36 with the other hand. Thisadditionally facilitates also unlocking of the holding arm 10. However,it often occurs in practice that the operator forgets this securitymeasure for supporting the holding arm 10 and is thus surprised that theholding arm 10 suddenly loses its stability during the unlockingprocedure and bags downwards. This renders handling of the holding arm10 difficult.

SUMMARY

It is the object of the invention to develop a manually operableunlocking device determined for a holding mechanism of theabove-mentioned type further such that the handling thereof becomeseasier and safer than has been the case so far.

The invention solves this object in that the conversion mechanismincludes an elastically deformable force limiter via which the forcetransfer element is coupled to the trigger and which prevents due to itselastic deformation the transfer of the operating force to the trigger,if the operating force exceeds a predetermined force.

The invention takes advantage of the fact that the operating force whichis to be manually exerted on the operating part in order to unlock theholding mechanism depends on the load to be supported, in particularbecomes larger as the load increases. This means that the force to beapplied in order to unlock the holding mechanism can be considered as ameasure for the load which is applied to the holding mechanism. Thecircumstance that the operating force becomes larger with increasingload also includes a security aspect to the effect that an accidentalunlocking in case of a large load is prevented.

The invention provides an elastically deformable force limiter whichonly allows a transfer of the operating force manually exerted on theoperating part to the trigger, if the operating force is not larger thana predetermined force. As the operating force, as explained above, is ameasure for the load resting on the holding mechanism, the force limiterprevents a transfer of the operating force to the trigger and thusunlocking of the holding mechanism to which the load is applied, if thisload exceeds a predetermined value. Conversely, this means thatunlocking of the holding mechanism only by operating of the operatingpart is only possible according to the invention, if the load is notlarger than this predetermined value.

If the operator operates the operating part and in doing so realizesthat in this way unlocking of the holding mechanism is not possible forhim, the operator becomes aware that the load resting on the holdingmechanism is larger than the predetermined value. After the operator hasrealized that, he can for example, while continuing to exert theoperating force on the operating part, support with the same or hisother hand the holding mechanism, in order to counteract the loadresting on the holding mechanism and thus to unload the holdingmechanism. If the holding mechanism is sufficiently unloaded in thismanner, it becomes possible for the operator to unlock the holdingmechanism by exerting the operating force on the operating part. Therebyit is reliably prevented that the operator is surprised by a suddentransfer of the holding mechanism from a load holding state to a loadyielding state. Further, by the limitation of the effective operatingforce damage of the unlocking device and/or the parts forming theholding mechanism as a consequence of an excessive force application isprevented. Finally, by limiting the operating force good ergonomics ofthe handle operation is guaranteed.

In a preferred embodiment, the force limiter is a spring, the restoringforce of which is dimensioned such that the spring maintains itsoriginal shape, if the operating force is smaller or equal to thepredetermined force, and that the spring is elastically deformed, if theoperating force exceeds the predetermined force. If the operating forceis sufficiently small, the spring interconnected between the forcetransfer element and the trigger acts as a substantially rigid element,so that the operating force exerted on the operating part acts via thespring largely unweakened on the trigger and the holding mechanism isunlocked. If, however, the operating force exerted on the operating partis that large, that the operator should unload the holding mechanismbefore its unlocking, in order not to be surprised by the suddenlyoccurring instability of the holding mechanism, the spring absorbs as aconsequence of its elastic deformation quasi the exerted operatingforce, whereby the latter does not act on the trigger anymore and theholding mechanism remains locked. Only with unloading of the holdingmechanism the operating force to be exerted on the operating partbecomes so small again that this does not cause an elastic deformationof the spring and the operating force is transferred to the trigger.

Preferably, the spring is a pressure spring, which is compressed betweenthe force transfer element and the trigger, if the force exerted on theoperating part is larger than the predetermined force.

In a preferred embodiment, the conversion mechanism comprises a firsttoothing formed at the operating part and a second toothing formed atthe force transfer element which meshes with the first toothing. Such atransmission formed by two toothing patterns is particularly suitable toconvert an operation of the operating part e.g. in a linear movement ofthe force transfer element and thus in a corresponding movement of thetrigger coupled via the force limiter to the force transfer element (asfar as the operating force does not exceed a predetermined force).

In an alternative embodiment, the conversion mechanism comprises amovable pressing surface formed at the operating part and a toggle leverwith a longer first leg and a shorter second leg, wherein the longerfirst leg of the toggle lever is supported at one end in a first centerof rotation stationary inside the unlocking device, the shorter secondleg of the toggle lever is rotatably supported at one end in a secondcenter of rotation, which is stationary relative to the movably guidedforce transfer element, the two legs are supported respectively at theirother end in a common third center of rotation, and the pressing surfacepresses onto the toggle lever in the region of the third centre ofrotation when the operating part is manually operated. By using a togglelever a delayed transmission of the operating force at constantoperating speed can be obtained. This means that at constant operatingspeed the stroke speed, with which the force transfer element is moved,decreases, while the force exerted by the force transfer elementincreases. Thus, the operating force exerted by the operator comes intoeffect with delay, so that the operator can better prepare for thecoming unlocking of the holding mechanism when operating the operatingpart. Further, in this manner a larger force transmission becomespossible.

Preferably, the force transfer element includes a hollow cylindricalportion in which the force limiter is supported. This allows aparticularly compact construction of the unlocking device. The triggercomprises for example a trigger rod which is linearly guided in thedirection of its longitudinal axis. In this case, the trigger rod can beat least partially guided inside the oblong force limiter. If the forcelimiter is e.g. a coil spring, in this embodiment a part of the triggerrod extends into the interior of the coil spring. This also favours aparticularly compact construction of the unlocking device.

Preferably, an end stop is provided, which limits the elasticdeformation of the force limiter. If the force limiter is for example acompression spring, the end stop guarantees that the compression springis only compressed so tightly that the spring deflection caused therebyis still within an operating region determined by a pre-definedspring-load deflection curve. This ensures that the spring can fulfillits function, i.e. either allowing or preventing the transfer of theoperating force exerted on the operating part, depending on the size ofsaid force, to the trigger reliably for a long period of time.

The above-mentioned end stop is for example an end stop surface whichabuts the force transfer element. In this embodiment, the end stoplimits the lifting of the force transfer element. It is however alsopossible to assign the end stop for example to the operating part torestrict the operating path thereof.

According to a further aspect of the invention a holding mechanism towhich a load can be applied is provided which comprises an unlockingdevice of the above-described type.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be explained in the following on the basis of theFigures, wherein:

FIG. 1 shows a conventional holding arm for supporting a patient's arm;

FIG. 2 shows a longitudinal section through an unlocking device usablefor the holding arm according to FIG. 1 according to the firstembodiment in a state in which a handle of the unlocking device is notoperated and the holding arm is locked;

FIG. 3 shows a longitudinal section through the unlocking deviceaccording to FIG. 2 in a state in which the handle is operated and as aresult the holding arm is unlocked;

FIG. 4 shows a longitudinal section through the unlocking deviceaccording to FIG. 2 in a state in which the handle is operated and theholding arm still remains locked;

FIG. 5 shows a longitudinal section through a locking device usable forthe holding arm according to FIG. 1 according to the second embodimentin a state in which the handle of the locking device is not operated andthe holding arm is locked;

FIG. 6 shows a longitudinal section through the unlocking deviceaccording to FIG. 5 in a state in which the handle is operated and theholding arm is unlocked; and

FIG. 7 shows a longitudinal section through the unlocking deviceaccording to FIG. 5 in a state in which the handle is operated and theholding arm still remains locked.

DETAILED DESCRIPTION

FIG. 2 shows an unlocking device 50 in a longitudinal section as firstembodiment. The unlocking device 50 is suited to unlock the holding arm10 shown in FIG. 1 in the manner described below.

The unlocking device 50 has an elongated housing 52 which is formed fromtwo housing parts 54 and 56 being coupled together via screwedconnections 58 and 60. The unlocking device 50 further includes a handle62 being manually operable by an operator, a conversion mechanismgenerally referred to with 64 in FIG. 2 and a trigger rod 66 movablyguided along the housing longitudinal axis. The conversion mechanism 64is formed by a transmission in the first embodiment which comprises atoothed wheel portion 68 formed at the handle 62 and a toothed rack 70meshed with the toothed wheel portion 68. The toothed rack 70 is part ofa force transfer element 72 which includes a hollow cylindrical portion74 at the end thereof facing away from the toothed rack 70.

At the end of the trigger rod 66 facing the handle 62 a support 76 isinstalled which together with a rigid, hollow cylindrical end stop 78defines a space in which a pressure loadable coil spring 80 is arranged.

The trigger rod 66 extends through a through bore 82 formed in thehousing part 56. Thereby, the trigger rod 66 is movably guided in thedirection of the longitudinal axis of the housing 52. The trigger rod 66serves to operate an unlocking mechanism which is included in theholding arm not shown in FIG. 2. Of this unlocking mechanism in FIG. 2only a single unlocking component 84 is illustrated which is pivotablysupported about a pivoting axis 86. Due to the trigger rod 66 pressingonto the unlocking component 84 the latter is moved about the pivotingaxis 86 for unlocking the holding arm.

The coil spring 80 via which the force transfer element 72 is coupled tothe trigger rod 66 forms a force limiter which ensures that theoperating force manually exerted by the operator on the handle 62 isonly transferred via the conversion mechanism 65 to the trigger rod 66and thus to the unlocking component 84, if the operating force does notexceed a predetermined force.

The spring force with which the coil spring 80 counteracts itscompression is selected exactly such that the coil spring 80 is onlycompressed, if the operating fore exceeds the predetermined force. Inthis case, the coil spring 80 quasi absorbs the operating force exertedvia the handle 62 on the force transfer element 72 by being elasticallycompressed. If the operating force is, however, smaller or equal to thepredetermined force, it is not sufficient to compress the coil screw 80.The coil screw 80 then forms a rigid coupling element between the forcetransfer element 72 and the trigger rod 66, so that the movement of theforce transfer element 72 caused by operating the handle 62 is convertedinto a corresponding movement of the trigger rod 66 in the direction ofthe longitudinal axis of the housing 52 causing the unlocking component84 to be moved about the pivoting axis 86 and ultimately the holding armto be unlocked.

FIGS. 2 to 4 illustrate the mode of operation of the unlocking device50, in particular of the force limiter formed by the coil spring 80.

In FIG. 2, the handle 62 is not operated. Correspondingly the triggerrod 66 remains in its locking position in which it does not act on theunlocking component 84. The holding arm is unlocked.

In FIG. 3, the handle 62 is operated with a (load dependent) operatingforce, which is not sufficient to compress the coil screw 80significantly. Thus, in this state the coil screw 80 forms asubstantially rigid element which is moved together with the forcetransfer element 72 in the direction of the longitudinal axis of thehousing 52 downwards until the hollow cylindrical portion 74 of theforce transfer element 72 abuts the rigid end stop 78. Thus, theoperating force is transferred to the trigger rod 66 causing it to bemoved in its unlocking position and the unlocking component 84 to bepivoted about the pivoting axis 86. The holding arm is unlocked.

In FIG. 4, the handle 62 is operated with a (load dependent) operatingforce, which is large enough to compress the coil spring 80. The coilspring 80 thus absorbs the exerted operating force causing the triggerrod 62 to remain in its locking position and not to act on the unlockingcomponent 84. The holding arm 62 remains locked despite of the operationof the handle 62.

In FIGS. 5 to 7, a modification of the unlocking device 50 isillustrated as a second embodiment. The second embodiment differs fromthe first embodiment shown in FIGS. 2 to 4 only by a modified conversionmechanism, which is referred to with 90 in FIGS. 5 to 7. Said componentsof the second embodiment which correspond in their function with thoseof the first embodiment are provided with the reference signs used inthe first embodiment.

The conversion mechanism 90 modified with respect to the firstembodiment includes a toggle lever 92, which is formed from a longerfirst leg 94 and a shorter second leg 96. The first leg 94 is supportedwith one end at a pivot axis 98 which is rigidly installed in thehousing 52. The pivoting axis 98 thus forms a first center of rotationof the toggle lever 92 stationary relative to the housing 52. The secondleg 96 is supported with its end facing away from the first leg 94 at apivoting axis 100, which is rigidly installed at the force transferelement 72, which is movable in the direction of the longitudinal axisof the housing 52. The pivoting axis 100 thus forms a second center ofrotation which is moved together with the force transfer element 72.

At the ends thereof facing each other the two legs 94 and 96 arerotatably coupled to each other. For this, the second leg 96 includes anapproximately spherical portion 102, which is supported in acorresponding spherical receptacle, which is formed at the end of thefirst leg 94 a facing the second leg. By this rotatable coupling of thetwo legs 94 and 96 a common movable third center of rotation of thetoggle lever 92 is given.

The toggle lever 92 abuts in the region of its third center of rotationa pressing surface 104 formed at the handle 62. If the operator operatesthe handle 62, the two legs 94 and 96 are, as shown in FIG. 6, alignedvertically bringing the toggle lever 92 altogether in a form in which itis positioned approximately parallel to the longitudinal axis of thehousing 92. By this alignment of the toggle lever 92 the operating forceexerted on the handle 62 is transferred to the force transfer element 72causing it to be moved downwards in the direction of the longitudinalaxis of the housing 52 (in FIGS. 5 to 7).

Besides, the second embodiment shown in FIGS. 5 to 7 operates in thesame manner as the first embodiment according to FIGS. 2 to 4. For thatmatter, the state shown in FIG. 5 in which the handle 62 is not operatedand the holding arm is consequently locked corresponds to the stateaccording to FIG. 2, while the state illustrated in FIG. 6 in which thehandle 62 is operated and the holding arm is unlocked corresponds to thestate according to FIG. 3 and the state shown in FIG. 7 in which thehandle 62 is operated, but the holding arm remains locked corresponds tothe state according to FIG. 4.

Although various embodiments of the present invention have beendescribed and shown, the invention is not restricted thereto, but mayalso be embodied in other ways within the scope of the subject-matterdefined in the following claims.

What is claimed is:
 1. A device for manually unlocking a holdingmechanism to which a load can be applied, comprising: an operatingelement which is to be operated manually for unlocking the holdingmechanism with an operating force becoming larger as the load increases,a conversion mechanism which includes a force transfer element coupledto the operating element, and a trigger coupled to the force transferelement, wherein in order to unlock the holding mechanism the trigger ismovable by the operating force transferred by the force transfer elementto the trigger from a locked position in which the trigger isoperatively decoupled from the holding mechanism into an unlockedposition in which the trigger is operatively coupled to the holdingmechanism for unlocking said holding mechanism, wherein the conversionmechanism includes an elastically deformable force limiter via which theforce transfer element is coupled to the trigger and which prevents dueto the elastic deformation thereof the transfer of the operating forceto the trigger, if the operating force exceeds a predetermined force. 2.The device according to claim 1, wherein an elongated housing, in whichthe conversion mechanism converts the operating force manually exertedon the operating element into a movement of the force transfer elementalong a housing longitudinal axis and the force limiter is elasticallydeformable along the housing longitudinal axis.
 3. The device accordingto claim 1, wherein the force limiter is a spring, the restoring forceof which is dimensioned such that the spring maintains its originalform, if the operating force is less than or equal to the predeterminedforce, and that the spring deforms elastically, if the operating forceexceeds the predetermined force.
 4. The device according to claim 3,wherein the spring is formed as pressure spring.
 5. The device accordingto claim 1, wherein the conversion mechanism comprises a first toothingformed at the operating element and a second toothing formed at theforce transfer element which is meshed with the first toothing.
 6. Thedevice according to claim 1, wherein the conversion mechanism comprisesa pressing surface formed at the operating element and a toggle leverhaving a longer first leg and a shorter second leg, the longer first legof the toggle lever is rotatably supported at one end in a first centerof rotation stationary inside the device, the shorter second leg of thetoggle lever is rotatably supported at one end in a second center ofrotation which is stationary relative to the movably guided forcetransfer element, the two legs are rotatably supported respectively attheir other end in a common third center of rotation, and the pressingsurface during manual operation of the operating element presses ontothe toggle lever in the region of the third center of rotation.
 7. Thedevice according to claim 1, wherein the operating element is apivotably supported handle.
 8. The device according to claim 1, whereinthe force transfer element includes a hollow cylindrical portion inwhich the force limiter is supported.
 9. The device according to claim1, wherein the trigger comprises a trigger rod which is linearly guidedin the direction of the longitudinal axis thereof.
 10. The deviceaccording to claim 9, wherein the trigger rod is guided at leastpartially inside the oblong force limiter.
 11. The device according toclaim 1, wherein an end stop which limits the elastic deformation of theforce limiter.
 12. The device according to claim 11, wherein the endstop is formed by an end stop surface that abuts the force transferelement.
 13. A holding mechanism to which a load can be applied,comprising a device for unlocking said holding mechanism according toclaim
 1. 14. The holding mechanism according to claim 13, wherein theholding mechanism is a holding arm formed for supporting a body portionof a patient, which has at least two rigid holding members and a joint,which connects the two holding members together, and an unlockingmechanism, which cooperates with the trigger such that the joint rigidlycouples the two holding members together in the locking position of thetrigger and movably couples the two holding members in the unlockingposition of the trigger.
 15. The device according to claim 2, whereinthe force limiter is a spring, the restoring force of which isdimensioned such that the spring maintains its original form, if theoperating force is less than or equal to the predetermined force, andthat the spring deforms elastically, if the operating force exceeds thepredetermined force.
 16. The device according to claim 2, wherein theconversion mechanism comprises a pressing surface formed at theoperating element and a toggle lever having a longer first leg and ashorter second leg, the longer first leg of the toggle lever isrotatably supported at one end in a first center of rotation stationaryinside the device, the shorter second leg of the toggle lever isrotatably supported at one end in a second center of rotation which isstationary relative to the movably guided force transfer element, thetwo legs are rotatably supported respectively at their other end in acommon third center of rotation, and the pressing surface during manualoperation of the operating element presses onto the toggle lever in theregion of the third center of rotation.
 17. The device according toclaim 3, wherein the conversion mechanism comprises a pressing surfaceformed at the operating element and a toggle lever having a longer firstleg and a shorter second leg, the longer first leg of the toggle leveris rotatably supported at one end in a first center of rotationstationary inside the device, the shorter second leg of the toggle leveris rotatably supported at one end in a second center of rotation whichis stationary relative to the movably guided force transfer element, thetwo legs are rotatably supported respectively at their other end in acommon third center of rotation, and the pressing surface during manualoperation of the operating element presses onto the toggle lever in theregion of the third center of rotation.
 18. The device according toclaim 4, wherein the conversion mechanism comprises a pressing surfaceformed at the operating element and a toggle lever having a longer firstleg and a shorter second leg, the longer first leg of the toggle leveris rotatably supported at one end in a first center of rotationstationary inside the device, the shorter second leg of the toggle leveris rotatably supported at one end in a second center of rotation whichis stationary relative to the movably guided force transfer element, thetwo legs are rotatably supported respectively at their other end in acommon third center of rotation, and the pressing surface during manualoperation of the operating element presses onto the toggle lever in theregion of the third center of rotation.